Population Movements And Genetics - IELTS Reading Answers & Explanations
From Cambridge IELTS 07 Academic Reading Test 3 · Part 2 · Questions 14–26
Reading Passage
You should spend about 20 minutes on Questions 14-26, which are based on Reading Passage 2 on the following pages.
Population movements and genetics
A Study of the origins and distribution of human populations used to be based on archaeological and fossil evidence. A number of techniques developed since the 1950s, however, have placed the study of these subjects on a sounder and more objective footing. The best information on early population movements is now being obtained from the 'archaeology of the living body', the clues to be found in genetic material.
B Recent work on the problem of when people first entered the Americas is an example of the value of these new techniques. North-east Asia and Siberia have long been accepted as the launching ground for the first human colonisers of the New World1. But was there one major wave of migration across the Bering Strait into the Americas, or several? And when did this event, or events, take place? In recent years, new clues have come from research into genetics, including the distribution of genetic markers in modern Native Americans2.
C An important project, led by the biological anthropologist Robert Williams, focused on the variants (called Gm allotypes) of one particular protein – immunoglobin G – found in the fluid portion of human blood. All proteins 'drift', or produce variants, over the generations, and members of an interbreeding human population will share a set of such variants. Thus, by comparing the Gm allotypes of two different populations (e.g. two Indian tribes), one can establish their genetic 'distance', which itself can be calibrated to give an indication of the length of time since these populations last interbred.
D Williams and his colleagues sampled the blood of over 5,000 American Indians in western North America during a twenty-year period. They found that their Gm allotypes could be divided into two groups, one of which also corresponded to the genetic typing of Central and South American Indians. Other tests showed that the Inuit (or Eskimo) and Aleut3 formed a third group. From this evidence it was deduced that there had been three major waves of migration across the Bering Strait. The first, Paleo-Indian, wave more than 15,000 years ago was ancestral to all Central and South American Indians. The second wave, about 14,000-12,000 years ago, brought Na-Dene hunters, ancestors of the Navajo and Apache (who only migrated south from Canada about 600 or 700 years ago). The third wave, perhaps 10,000 or 9,000 years ago, saw the migration from North-east Asia of groups ancestral to the modern Eskimo and Aleut.
E How far does other research support these conclusions? Geneticist Douglas Wallace has studied mitochondrial DNA4 in blood samples from three widely separated Native American groups: Pima-Papago Indians in Arizona, Maya Indians on the Yucatán peninsula, Mexico, and Ticuna Indians in the Upper Amazon region of Brazil. As would have been predicted by Robert Williams's work, all three groups appear to be descended from the same ancestral (Paleo-Indian) population.
F There are two other kinds of research that have thrown some light on the origins of the Native American population; they involve the study of teeth and of languages. The biological anthropologist Christy Turner is an expert in the analysis of changing physical characteristics in human teeth. He argues that tooth crowns and roots5 have a high genetic component, minimally affected by environmental and other factors. Studies carried out by Turner of many thousands of New and Old World specimens, both ancient and modern, suggest that the majority of prehistoric Americans are linked to Northern Asian populations by crown and root traits such as incisor6 shoveling (a scooping out on one or both surfaces of the tooth), single-rooted upper first premolars6 and triple-rooted lower first molars6. According to Turner, this ties in with the idea of a single Paleo-Indian migration out of North Asia, which he sets at before 14,000 years ago by calibrating rates of dental micro-evolution. Tooth analyses also suggest that there were two later migrations of Na-Denes and Eskimo-Aleut.
G The linguist Joseph Greenberg has, since the 1950s, argued that all Native American languages belong to a single 'Amerind' family, except for Na-Dene and Eskimo-Aleut – a view that gives credence to the idea of three main migrations. Greenberg is in a minority among fellow linguists, most of whom favour the notion of a great many waves of migration to account for the more than 1,000 languages spoken at one time by American Indians. But there is no doubt that the new genetic and dental evidence provides strong backing for Greenberg's view. Dates given for the migrations should nevertheless be treated with caution, except where supported by hard archaeological evidence.
1 New World: the American continent, as opposed to the so-called Old World of Europe, Asia and Africa
2 modern Native American: an American descended from the groups that were native to America
3 Inuit and Aleut: two of the ethnic groups native to the northern regions of North America (i.e. northern Canada and Greenland)
4 DNA: the substance in which genetic information is stored
5 crown/root: parts of the tooth
6 incisor/premolar/molar: kinds of teeth
Questions
Questions 14–19 Matching Headings
Reading Passage 2 has seven sections, A-G.
Choose the correct headings for sections A-F from the list of headings below.
i. The results of the research into blood-variants
ii. Dental evidence
iii. Greenberg's analysis of the dental and linguistic evidence
iv. Developments in the methods used to study early population movements
v. Indian migration from Canada to the U.S.A.
vi. Further genetic evidence relating to the three-wave theory
vii. Long-standing questions about prehistoric migration to America
viii. Conflicting views of the three-wave theory, based on non-genetic evidence
ix. Questions about the causes of prehistoric migration to America
x. How analysis of blood-variants measures the closeness of the relationship between different populations
Questions 20–21 Table Completion
The discussion of Williams's research indicates the periods at which early people are thought to have migrated along certain routes. There are six routes, A-F, marked on the map below.
Complete the table below.
| Route | Period (number of years ago) |
|---|---|
| 20 | 15,000 or more |
| 21 | 600 to 700 |
Questions 22–25 Matching Features
Reading Passage 2 refers to the three-wave theory of early migration to the Americas. It also suggests in which of these three waves the ancestors of various groups of modern native Americans first reached the continent.
Classify the groups named in the table below as originating from
A. the first wave
B. the second wave
C. the third wave
Questions 26–26 Multiple Choice (One Answer)
Choose the correct letter, A, B, C or D.
Answers & Explanations Summary
| # | Answer | Evidence | Explanation |
|---|---|---|---|
| Q14 | iv | Study of the origins and distribution of human populations used to be based on archaeological and fossil evidence. A number of techniques developed since the 1950s, however, have placed the study of these subjects on a sounder and more objective footing | Excerpt/Passage Explanation: The passage states that learning about where people came from used to depend on looking at old bones and ancient items. However, since the 1950s, new scientific ways of studying these things have been made that are more accurate and reliable. Answer Explanation: The answer means that the first part of the text explains how the ways scientists study the movement of ancient groups of people have changed and improved over time. Reason For Correctness: The correct answer is 'iv' because Section A describes the shift in how researchers study history. It explains that while they used to rely only on old objects (archaeology) and bones (fossils), new and better methods involving genetics have been created since the 1950s. These changes are the 'developments' mentioned in the heading, and the focus is on the 'methods' or tools used to learn about 'early population movements' (how people moved around the world a long time ago). |
| Q15 | vii | North-east Asia and Siberia have long been accepted as the launching ground for the first human colonisers of the New World1. But was there one major wave of migration across the Bering Strait into the Americas, or several? And when did this event, or events, take place | Excerpt/Passage Explanation: The passage states that people have known for a long time where the first travelers came from, but they still have big questions about how many groups came across and when exactly it happened. These are the "long-standing questions" mentioned in the heading. Answer Explanation: The answer vii means that Section B focuses on old, unanswered questions about how humans moved to the Americas in ancient times. Reason For Correctness: The correct answer is vii because Section B identifies specific, unresolved issues regarding the migration of people to the Americas. While it notes that North-east Asia and Siberia have "long been accepted" as the origin point, it introduces several questions that researchers have struggled with for a long time, such as whether there was "one major wave... or several" and "when" these migrations happened. This matches the heading "Long-standing questions about prehistoric migration to America." Key terms like "first human colonisers" relate to "prehistoric migration." |
| Q16 | x | Thus, by comparing the Gm allotypes of two different populations (e.g. two Indian tribes), one can establish their genetic 'distance', which itself can be calibrated to give an indication of the length of time since these populations last interbred | Excerpt/Passage Explanation: The passage explains that by looking at certain blood protein types from two groups, scientists can find out their genetic 'distance.' This number shows how much time has passed since the two groups were one single group. Answer Explanation: The answer means that Section C explains a method for checking blood to see how closely two groups of people are related. Reason For Correctness: The correct answer is heading 'x' because Section C focuses on the work of Robert Williams, who examined 'Gm allotypes' (variants of a blood protein). The passage explains that by looking at these blood variants in different groups, scientists can calculate 'genetic distance.' This distance is a way to measure how closely related the groups are and how long it has been since they were part of the same population. |
| Q17 | i | They found that their Gm allotypes could be divided into two groups, one of which also corresponded to the genetic typing of Central and South American Indians. Other tests showed that the Inuit (or Eskimo) and Aleut3 formed a third group. From this evidence it was deduced that there had been three major waves of migration across the Bering Strait | Excerpt/Passage Explanation: The passage explains that scientists discovered three distinct groups in the blood they studied. Because of these findings, they concluded that people traveled to the Americas in three large, separate groups at different times. Answer Explanation: The answer 'i' refers to the findings or outcomes discovered by scientists after testing and analyzing different types of blood. Reason For Correctness: The correct answer is 'i' because Section D describes what Robert Williams and his team learned after spending twenty years studying the blood of thousands of people. The section explains that they found three specific groups based on 'Gm allotypes' (which are variants or types of blood proteins). These findings, or 'results', led the scientists to conclude that there were three main trips (waves) of people moving to America in the past. |
| Q18 | vi | Geneticist Douglas Wallace has studied mitochondrial DNA4 in blood samples from three widely separated Native American groups: Pima-Papago Indians in Arizona, Maya Indians on the Yucatán peninsula, Mexico, and Ticuna Indians in the Upper Amazon region of Brazil. As would have been predicted by Robert Williams's work, all three groups appear to be descended from the same ancestral (Paleo-Indian) population | Excerpt/Passage Explanation: The passage explains that another scientist, Douglas Wallace, looked at DNA from three different groups of native people living in different places. His findings agreed with the earlier research, showing that all these people came from the same original group of ancestors. Answer Explanation: The answer identifies Section E as a part of the text that provides more genetic proof to support the idea that people migrated to the Americas in three distinct groups (the three-wave theory). Reason For Correctness: The correct answer is 'vi' because Section E introduces the work of geneticist Douglas Wallace. He used a different type of genetic testing (mitochondrial DNA) on various groups of Native Americans. His results showed that these groups shared the same ancestors, which matches (supports) the conclusions made in the previous section about there being three main waves of migration. This counts as 'further genetic evidence' because it follows the first genetic study mentioned in Section C and D. |
| Q19 | ii | There are two other kinds of research that have thrown some light on the origins of the Native American population; they involve the study of teeth and of languages. The biological anthropologist Christy Turner is an expert in the analysis of changing physical characteristics in human teeth | Excerpt/Passage Explanation: The passage states that Section F covers research involving teeth and languages. It specifically introduces Christy Turner, an expert who looks at how human teeth change to understand where people originally came from. Answer Explanation: The answer is the second heading from the list: "Dental evidence". Reason For Correctness: The correct answer is heading "ii" because Section F is primarily focused on the research and findings related to human teeth (dental features). It explains how an expert named Christy Turner studied different parts of the teeth, such as crowns and roots, to find connections between prehistoric Americans and Asian populations. The keywords "teeth", "tooth", and "dental" are mentioned multiple times throughout the section to show that this is the main topic. |
| Q20 | E | The first, Paleo-Indian, wave more than 15,000 years ago was ancestral to all Central and South American Indians | Excerpt/Passage Explanation: The passage explains that the very first group of people traveled across more than fifteen thousand years ago, and these people are the ancestors of everyone in Central and South America. Answer Explanation: The answer E is the name of a specific route (a path of travel) used by the first group of people who moved to the Americas at least 15,000 years ago. Reason For Correctness: The correct answer is E because paragraph D discusses the research of Williams and explains that the earliest people to migrate arrived "more than 15,000 years ago." This group is called the "Paleo-Indian" wave, and in the context of the map associated with this question, Route E represents their path as they traveled to become the ancestors of people in Central and South America. Key phrases to look for are "first wave" and "more than 15,000 years ago." |
| Q21 | D | ancestors of the Navajo and Apache (who only migrated south from Canada about 600 or 700 years ago) | Excerpt/Passage Explanation: The passage explains that the people who were related to the Navajo and Apache from a long time ago moved from Canada to more southern places about 600 or 700 years ago. Answer Explanation: The answer D refers to the label on a map that shows a specific movement of people (a migration route) that occurred around 600 to 700 years ago. Reason For Correctness: The correct answer is D because the text in Paragraph D describes research into population movements. It specifically mentions that the relatives of the Navajo and Apache people moved or 'migrated' from Canada to the south during the '600 or 700 years ago' time period. This matches the period provided in the table, and the route 'D' on the map represents this movement. |
| Q22 | C | Other tests showed that the Inuit (or Eskimo) and Aleut formed a third group The third wave, perhaps 10,000 or 9,000 years ago, saw the migration from North-east Asia of groups ancestral to the modern Eskimo and Aleut |
Excerpt/Passage Explanation: The passage confirms that Inuit and Eskimo are names for the same people. It states that this group is linked to the third wave of individuals who traveled from Asia to the Americas. Answer Explanation: The answer C means that the Inuit people moved to the Americas during the third period (or wave) of travel. Reason For Correctness: The correct answer is C because the text describes three different times (waves) when groups of people moved to the Americas. By studying blood and genetic clues, researchers found that the Inuit—also referred to as Eskimo—were in a group separate from the others. The passage specifically identifies this group as being part of the third wave of travelers who arrived between 9,000 and 10,000 years ago. |
| Q23 | B | The second wave, about 14,000-12,000 years ago, brought Na-Dene hunters, ancestors of the Navajo and Apache (who only migrated south from Canada about 600 or 700 years ago) | Excerpt/Passage Explanation: The passage explains that the second group of people to arrive in the Americas were the Na-Dene hunters. These hunters are the old family of the people we now call the Navajo and the Apache. Answer Explanation: The answer is B, which means the Apache people are part of the second group (or 'wave') of humans who moved into the Americas a long time ago. Reason For Correctness: The correct answer is B because the text in Paragraph D explains that there were three main times when groups of people moved across the Bering Strait. It clearly says that the second time this happened, it involved 'Na-Dene hunters.' These hunters were the ancestors—the early family members—of the Apache group. |
| Q24 | A | The first, Paleo-Indian, wave more than 15,000 years ago was ancestral to all Central and South American Indians Geneticist Douglas Wallace has studied mitochondrial DNA4 in blood samples from three widely separated Native American groups: Pima-Papago Indians in Arizona, Maya Indians on the Yucatán peninsula, Mexico, and Ticuna Indians in the Upper Amazon region of Brazil. As would have been predicted by Robert Williams's work, all three groups appear to be descended from the same ancestral (Paleo-Indian) population |
Excerpt/Passage Explanation: The passage explains that the very first group of people to move to the Americas was the Paleo-Indian wave. It then mentions that scientific tests on the Pima-Papago people show they come from that same original Paleo-Indian group. Answer Explanation: The answer means that the group of people called the Pima-Papago first came to the Americas during the very first movement of people across the land. Reason For Correctness: The correct answer is A because the text links the Pima-Papago group to the 'Paleo-Indian' population through genetic research. In Paragraph D, the passage explicitly describes the 'Paleo-Indian' migration as the 'first wave'. Since the Pima-Papago are descended from this specific group, they are classified as being part of that first movement. |
| Q25 | A | Geneticist Douglas Wallace has studied mitochondrial DNA4 in blood samples from three widely separated Native American groups: Pima-Papago Indians in Arizona, Maya Indians on the Yucatán peninsula, Mexico, and Ticuna Indians in the Upper Amazon region of Brazil. As would have been predicted by Robert Williams's work, all three groups appear to be descended from the same ancestral (Paleo-Indian) population The first, Paleo-Indian, wave more than 15,000 years ago was ancestral to all Central and South American Indians |
Excerpt/Passage Explanation: The passage explains that tests on the DNA of Ticuna Indians show they are part of the ‘Paleo-Indian’ family. It then identifies the movement of the Paleo-Indian family as the ‘first wave’ of people coming to the continent. Answer Explanation: The answer is 'A', which means that the Ticuna people moved to the Americas as part of the very first group of human travelers. Reason For Correctness: The correct answer is 'A' because the passage links the Ticuna people to the 'Paleo-Indian' group. In paragraph E, it says research on the Ticuna shows they are descended from (come from) the Paleo-Indian population. In paragraph D, the text clearly states that the 'Paleo-Indian' wave was the 'first' wave of migration. |
| Q26 | A | Studies carried out by Turner of many thousands of New and Old World specimens, both ancient and modern, suggest that the majority of prehistoric Americans are linked to Northern Asian populations by crown and root traits | Excerpt/Passage Explanation: The passage says that Turner looked at thousands of tooth samples from different parts of the world. He looked at old teeth and new teeth. His study found that most early Americans and people from Northern Asia have similar shapes in their teeth. Answer Explanation: The answer means that Christy Turner researched teeth from people who lived very long ago (prehistoric) and people living now (modern) in both the Americas and Asia. Reason For Correctness: The correct answer is supported by Paragraph F, which discusses Christy Turner's work. The paragraph states he is an expert in human teeth and that he studied thousands of teeth from the 'New World' (the Americas) and the 'Old World' (which includes Asia). The text mentions these samples were 'ancient' (prehistoric) and 'modern'. His research specifically looked for connections between early Americans and populations in Northern Asia. |